// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
 *******************************************************************************
 * Copyright (C) 1996-2010, International Business Machines Corporation and    *
 * others. All Rights Reserved.                                                *
 *******************************************************************************
 */
package com.ibm.icu.text;

import com.ibm.icu.impl.Utility;
import com.ibm.icu.impl.UtilityExtensions;
import java.util.List;

/**
 * A transliterator that is composed of two or more other transliterator objects linked together.
 * For example, if one transliterator transliterates from script A to script B, and another
 * transliterates from script B to script C, the two may be combined to form a new transliterator
 * from A to C.
 *
 * <p>Composed transliterators may not behave as expected. For example, inverses may not combine to
 * form the identity transliterator. See the class documentation for {@link Transliterator} for
 * details.
 *
 * <p>Copyright &copy; IBM Corporation 1999. All rights reserved.
 *
 * @author Alan Liu
 */
class CompoundTransliterator extends Transliterator {

    private Transliterator[] trans;

    private int numAnonymousRBTs = 0;

    /**
     * Constructs a new compound transliterator given an array of transliterators. The array of
     * transliterators may be of any length, including zero or one, however, useful compound
     * transliterators have at least two components.
     *
     * @param transliterators array of <code>Transliterator</code> objects
     * @param filter the filter. Any character for which {@code filter.contains()} returns {@code
     *     false} will not be altered by this transliterator. If {@code filter} is {@code null} then
     *     no filtering is applied.
     */
    /*public CompoundTransliterator(Transliterator[] transliterators,
                                  UnicodeFilter filter) {
        super(joinIDs(transliterators), filter);
        trans = new Transliterator[transliterators.length];
        System.arraycopy(transliterators, 0, trans, 0, trans.length);
        computeMaximumContextLength();
    }*/

    /**
     * Constructs a new compound transliterator given an array of transliterators. The array of
     * transliterators may be of any length, including zero or one, however, useful compound
     * transliterators have at least two components.
     *
     * @param transliterators array of <code>Transliterator</code> objects
     */
    /*public CompoundTransliterator(Transliterator[] transliterators) {
        this(transliterators, null);
    }*/

    /**
     * Constructs a new compound transliterator.
     *
     * @param ID compound ID
     * @param direction either Transliterator.FORWARD or Transliterator.REVERSE
     * @param filter a global filter for this compound transliterator or null
     */
    /*public CompoundTransliterator(String ID, int direction,
                                  UnicodeFilter filter) {
        super(ID, filter);
        init(ID, direction, true);
    }*/

    /**
     * Constructs a new compound transliterator with no filter.
     *
     * @param ID compound ID
     * @param direction either Transliterator.FORWARD or Transliterator.REVERSE
     */
    /*public CompoundTransliterator(String ID, int direction) {
        this(ID, direction, null);
    }*/

    /**
     * Constructs a new forward compound transliterator with no filter.
     *
     * @param ID compound ID
     */
    /*public CompoundTransliterator(String ID) {
        this(ID, FORWARD, null);
    }*/

    /**
     * Package private constructor for Transliterator from a vector of transliterators. The caller
     * is responsible for fixing up the ID.
     */
    CompoundTransliterator(List<Transliterator> list) {
        this(list, 0);
    }

    CompoundTransliterator(List<Transliterator> list, int numAnonymousRBTs) {
        super("", null);
        trans = null;
        init(list, FORWARD, false);
        this.numAnonymousRBTs = numAnonymousRBTs;
        // assume caller will fixup ID
    }

    /**
     * Internal method for safeClone...
     *
     * @param id
     * @param filter2
     * @param trans2
     * @param numAnonymousRBTs2
     */
    CompoundTransliterator(
            String id, UnicodeFilter filter2, Transliterator[] trans2, int numAnonymousRBTs2) {
        super(id, filter2);
        trans = trans2;
        numAnonymousRBTs = numAnonymousRBTs2;
    }

    /**
     * Finish constructing a transliterator: only to be called by constructors. Before calling
     * init(), set trans and filter to NULL.
     *
     * @param id the id containing ';'-separated entries
     * @param direction either FORWARD or REVERSE
     * @param idSplitPoint the index into id at which the splitTrans should be inserted, if there is
     *     one, or -1 if there is none.
     * @param splitTrans a transliterator to be inserted before the entry at offset idSplitPoint in
     *     the id string. May be NULL to insert no entry.
     * @param fixReverseID if true, then reconstruct the ID of reverse entries by calling getID() of
     *     component entries. Some constructors do not require this because they apply a facade ID
     *     anyway.
     */
    /*private void init(String id,
                      int direction,
                      boolean fixReverseID) {
        // assert(trans == 0);

        Vector list = new Vector();
        UnicodeSet[] compoundFilter = new UnicodeSet[1];
        StringBuffer regenID = new StringBuffer();
        if (!TransliteratorIDParser.parseCompoundID(id, direction,
                 regenID, list, compoundFilter)) {
            throw new IllegalArgumentException("Invalid ID " + id);
        }

        TransliteratorIDParser.instantiateList(list);

        init(list, direction, fixReverseID);

        if (compoundFilter[0] != null) {
            setFilter(compoundFilter[0]);
        }
    }*/

    /**
     * Finish constructing a transliterator: only to be called by constructors. Before calling
     * init(), set trans and filter to NULL.
     *
     * @param list a vector of transliterator objects to be adopted. It should NOT be empty. The
     *     list should be in declared order. That is, it should be in the FORWARD order; if
     *     direction is REVERSE then the list order will be reversed.
     * @param direction either FORWARD or REVERSE
     * @param fixReverseID if true, then reconstruct the ID of reverse entries by calling getID() of
     *     component entries. Some constructors do not require this because they apply a facade ID
     *     anyway.
     */
    private void init(List<Transliterator> list, int direction, boolean fixReverseID) {
        // assert(trans == 0);

        // Allocate array
        int count = list.size();
        trans = new Transliterator[count];

        // Move the transliterators from the vector into an array.
        // Reverse the order if necessary.
        int i;
        for (i = 0; i < count; ++i) {
            int j = (direction == FORWARD) ? i : count - 1 - i;
            trans[i] = list.get(j);
        }

        // If the direction is UTRANS_REVERSE then we may need to fix the
        // ID.
        if (direction == REVERSE && fixReverseID) {
            StringBuilder newID = new StringBuilder();
            for (i = 0; i < count; ++i) {
                if (i > 0) {
                    newID.append(ID_DELIM);
                }
                newID.append(trans[i].getID());
            }
            setID(newID.toString());
        }

        computeMaximumContextLength();
    }

    /**
     * Return the IDs of the given list of transliterators, concatenated with ';' delimiting them.
     * Equivalent to the perlish expression join(';', map($_.getID(), transliterators).
     */
    /*private static String joinIDs(Transliterator[] transliterators) {
        StringBuffer id = new StringBuffer();
        for (int i=0; i<transliterators.length; ++i) {
            if (i > 0) {
                id.append(';');
            }
            id.append(transliterators[i].getID());
        }
        return id.toString();
    }*/

    /**
     * Returns the number of transliterators in this chain.
     *
     * @return number of transliterators in this chain.
     */
    public int getCount() {
        return trans.length;
    }

    /**
     * Returns the transliterator at the given index in this chain.
     *
     * @param index index into chain, from 0 to <code>getCount() - 1</code>
     * @return transliterator at the given index
     */
    public Transliterator getTransliterator(int index) {
        return trans[index];
    }

    /** Append c to buf, unless buf is empty or buf already ends in c. */
    private static void _smartAppend(StringBuilder buf, char c) {
        if (buf.length() != 0 && buf.charAt(buf.length() - 1) != c) {
            buf.append(c);
        }
    }

    /**
     * Override Transliterator: Create a rule string that can be passed to createFromRules() to
     * recreate this transliterator.
     *
     * @param escapeUnprintable if true then convert unprintable character to their hex escape
     *     representations, \\uxxxx or \\Uxxxxxxxx. Unprintable characters are those other than
     *     U+000A, U+0020..U+007E.
     * @return the rule string
     */
    @Override
    public String toRules(boolean escapeUnprintable) {
        // We do NOT call toRules() on our component transliterators, in
        // general.  If we have several rule-based transliterators, this
        // yields a concatenation of the rules -- not what we want.  We do
        // handle compound RBT transliterators specially -- those for which
        // compoundRBTIndex >= 0.  For the transliterator at compoundRBTIndex,
        // we do call toRules() recursively.
        StringBuilder rulesSource = new StringBuilder();
        if (numAnonymousRBTs >= 1 && getFilter() != null) {
            // If we are a compound RBT and if we have a global
            // filter, then emit it at the top.
            rulesSource
                    .append("::")
                    .append(getFilter().toPattern(escapeUnprintable))
                    .append(ID_DELIM);
        }
        for (int i = 0; i < trans.length; ++i) {
            String rule;

            // Anonymous RuleBasedTransliterators (inline rules and
            // ::BEGIN/::END blocks) are given IDs that begin with
            // "%Pass": use toRules() to write all the rules to the output
            // (and insert "::Null;" if we have two in a row)
            if (trans[i].getID().startsWith("%Pass")) {
                rule = trans[i].toRules(escapeUnprintable);
                if (numAnonymousRBTs > 1 && i > 0 && trans[i - 1].getID().startsWith("%Pass"))
                    rule = "::Null;" + rule;

                // we also use toRules() on CompoundTransliterators (which we
                // check for by looking for a semicolon in the ID)-- this gets
                // the list of their child transliterators output in the right
                // format
            } else if (trans[i].getID().indexOf(';') >= 0) {
                rule = trans[i].toRules(escapeUnprintable);

                // for everything else, use baseToRules()
            } else {
                rule = trans[i].baseToRules(escapeUnprintable);
            }
            _smartAppend(rulesSource, '\n');
            rulesSource.append(rule);
            _smartAppend(rulesSource, ID_DELIM);
        }
        return rulesSource.toString();
    }

    /**
     * @internal
     */
    @Override
    public void addSourceTargetSet(UnicodeSet filter, UnicodeSet sourceSet, UnicodeSet targetSet) {
        UnicodeSet myFilter = new UnicodeSet(getFilterAsUnicodeSet(filter));
        UnicodeSet tempTargetSet = new UnicodeSet();
        for (int i = 0; i < trans.length; ++i) {
            // each time we produce targets, those can be used by subsequent items, despite the
            // filter.
            // so we get just those items, and add them to the filter each time.
            tempTargetSet.clear();
            trans[i].addSourceTargetSet(myFilter, sourceSet, tempTargetSet);
            targetSet.addAll(tempTargetSet);
            myFilter.addAll(tempTargetSet);
        }
    }

    //    /**
    //     * Returns the set of all characters that may be generated as
    //     * replacement text by this transliterator.
    //     */
    //    public UnicodeSet getTargetSet() {
    //        UnicodeSet set = new UnicodeSet();
    //        for (int i=0; i<trans.length; ++i) {
    //            // This is a heuristic, and not 100% reliable.
    //            set.addAll(trans[i].getTargetSet());
    //        }
    //        return set;
    //    }

    /** Implements {@link Transliterator#handleTransliterate}. */
    @Override
    protected void handleTransliterate(Replaceable text, Position index, boolean incremental) {
        /* Call each transliterator with the same start value and
         * initial cursor index, but with the limit index as modified
         * by preceding transliterators.  The cursor index must be
         * reset for each transliterator to give each a chance to
         * transliterate the text.  The initial cursor index is known
         * to still point to the same place after each transliterator
         * is called because each transliterator will not change the
         * text between start and the initial value of cursor.
         *
         * IMPORTANT: After the first transliterator, each subsequent
         * transliterator only gets to transliterate text committed by
         * preceding transliterators; that is, the cursor (output
         * value) of transliterator i becomes the limit (input value)
         * of transliterator i+1.  Finally, the overall limit is fixed
         * up before we return.
         *
         * Assumptions we make here:
         * (1) contextStart <= start <= limit <= contextLimit <= text.length()
         * (2) start <= start' <= limit'  ;cursor doesn't move back
         * (3) start <= limit'            ;text before cursor unchanged
         * - start' is the value of start after calling handleKT
         * - limit' is the value of limit after calling handleKT
         */

        /**
         * Example: 3 transliterators. This example illustrates the mechanics we need to implement.
         * C, S, and L are the contextStart, start, and limit. gl is the globalLimit. contextLimit
         * is equal to limit throughout.
         *
         * <p>1. h-u, changes hex to Unicode
         *
         * <p>4 7 a d 0 4 7 a abc/u0061/u => abca/u C S L C S L gl=f->a
         *
         * <p>2. upup, changes "x" to "XX"
         *
         * <p>4 7 a 4 7 a abca/u => abcAA/u C SL C S L gl=a->b 3. u-h, changes Unicode to hex
         *
         * <p>4 7 a 4 7 a d 0 3 abcAA/u => abc/u0041/u0041/u C S L C S L gl=b->15 4. return
         *
         * <p>4 7 a d 0 3 abc/u0041/u0041/u C S L
         */
        if (trans.length < 1) {
            index.start = index.limit;
            return; // Short circuit for empty compound transliterators
        }

        // compoundLimit is the limit value for the entire compound
        // operation.  We overwrite index.limit with the previous
        // index.start.  After each transliteration, we update
        // compoundLimit for insertions or deletions that have happened.
        int compoundLimit = index.limit;

        // compoundStart is the start for the entire compound
        // operation.
        int compoundStart = index.start;

        int delta = 0; // delta in length

        StringBuilder log = null;
        /// CLOVER:OFF
        if (DEBUG) {
            log =
                    new StringBuilder(
                            "CompoundTransliterator{"
                                    + getID()
                                    + (incremental ? "}i: IN=" : "}: IN="));
            UtilityExtensions.formatInput(log, text, index);
            System.out.println(Utility.escape(log.toString()));
        }
        /// CLOVER:ON

        // Give each transliterator a crack at the run of characters.
        // See comments at the top of the method for more detail.
        for (int i = 0; i < trans.length; ++i) {
            index.start = compoundStart; // Reset start
            int limit = index.limit;

            if (index.start == index.limit) {
                // Short circuit for empty range
                /// CLOVER:OFF
                if (DEBUG) {
                    System.out.println(
                            "CompoundTransliterator["
                                    + i
                                    + ".."
                                    + (trans.length - 1)
                                    + (incremental ? "]i: " : "]: ")
                                    + UtilityExtensions.formatInput(text, index)
                                    + " (NOTHING TO DO)");
                }
                /// CLOVER:ON
                break;
            }

            /// CLOVER:OFF
            if (DEBUG) {
                log.setLength(0);
                log.append(
                        "CompoundTransliterator["
                                + i
                                + "="
                                + trans[i].getID()
                                + (incremental ? "]i: " : "]: "));
                UtilityExtensions.formatInput(log, text, index);
            }
            /// CLOVER:ON

            trans[i].filteredTransliterate(text, index, incremental);

            // In a properly written transliterator, start == limit after
            // handleTransliterate() returns when incremental is false.
            // Catch cases where the subclass doesn't do this, and throw
            // an exception.  (Just pinning start to limit is a bad idea,
            // because what's probably happening is that the subclass
            // isn't transliterating all the way to the end, and it should
            // in non-incremental mode.)
            if (!incremental && index.start != index.limit) {
                throw new RuntimeException(
                        "ERROR: Incomplete non-incremental transliteration by " + trans[i].getID());
            }

            /// CLOVER:OFF
            if (DEBUG) {
                log.append(" => ");
                UtilityExtensions.formatInput(log, text, index);
                System.out.println(Utility.escape(log.toString()));
            }
            /// CLOVER:ON

            // Cumulative delta for insertions/deletions
            delta += index.limit - limit;

            if (incremental) {
                // In the incremental case, only allow subsequent
                // transliterators to modify what has already been
                // completely processed by prior transliterators.  In the
                // non-incrmental case, allow each transliterator to
                // process the entire text.
                index.limit = index.start;
            }
        }

        compoundLimit += delta;

        // Start is good where it is -- where the last transliterator left
        // it.  Limit needs to be put back where it was, modulo
        // adjustments for deletions/insertions.
        index.limit = compoundLimit;

        /// CLOVER:OFF
        if (DEBUG) {
            log.setLength(0);
            log.append(
                    "CompoundTransliterator{" + getID() + (incremental ? "}i: OUT=" : "}: OUT="));
            UtilityExtensions.formatInput(log, text, index);
            System.out.println(Utility.escape(log.toString()));
        }
        /// CLOVER:ON
    }

    /**
     * Compute and set the length of the longest context required by this transliterator. This is
     * <em>preceding</em> context.
     */
    private void computeMaximumContextLength() {
        int max = 0;
        for (int i = 0; i < trans.length; ++i) {
            int len = trans[i].getMaximumContextLength();
            if (len > max) {
                max = len;
            }
        }
        setMaximumContextLength(max);
    }

    /** Temporary hack for registry problem. Needs to be replaced by better architecture. */
    public Transliterator safeClone() {
        UnicodeFilter filter = getFilter();
        if (filter != null && filter instanceof UnicodeSet) {
            filter = new UnicodeSet((UnicodeSet) filter);
        }
        return new CompoundTransliterator(getID(), filter, trans, numAnonymousRBTs);
    }
}
